; FGRAPH.LSP
; a simple, customizable AutoCAD command to draw arbitrary functional graphs
; (c) 1996 CR/LF GmbH, Essen/Germany, Custom AutoCAD Programming since 1986
; by Dietmar Rudolph
;
; Include the function to use at the line marked (1) in AutoLISP notation,
; edit the lines containing <...> according to your needs.
; Load the AutoLISP file using the APPLOAD command. Type GRAPH to run.
;
(defun c:graph (/ the_function lowerlimit upperlimit delta_x x)
  (defun the_function (x)
             ; insert the function to evaluate here, for instance
    (* x x)  ; (1)    this example draws the graph for y=x^2
  )

  (setq lowerlimit -3.0    ;<smallest x coordinate>
        upperlimit 3.0     ;<largest x coordinate>
        delta_x    0.1     ;<increment value>
        x lowerlimit)
  (command "_pline")
  (while (<= x upperlimit)
     (command (list x (the_function x)))
     (setq x (+ x delta_x))
  )
  (command "")
  (command "_pedit" "_last" "_spline" "")
  (princ)
)